1. Field of the Invention
The invention relates to a solenoid arrangement. The invention also relates to a valve arrangement.
2. Description of the Prior Art
One such solenoid arrangement is known from German Patent Disclosure DE 197 07 587 A1. A pressure-proof solenoid has, in addition to the pole tube, a coil for actuating an armature that is axially movably guided in an armature chamber of the pole tube. The pole tube essentially comprises the following: a pole piece—also called a pole core—which can be screwed into a valve housing via a central thread; a nonmagnetic adapter piece; and a tubular piece, which adjoins the adapter and is closed on the face end, on the side remote from the pole piece, by means of a component acting as a stroke limiter. The pole piece, the adapter piece, the tube piece, and the stroke limiter define the armature chamber for the armature that cooperates with the coil. The armature is connected to a tappet, which penetrates the pole piece in the axial direction and serves to actuate a valve slide of a hydraulic valve. The nonmagnetic adapter piece serves to divert the magnetic flux into the armature. This nonmagnetic adapter piece can be embodied in annular-conical form, for attaining a favorable characteristic force-travel curve. In the production, however, such shaping involves effort and expense. Especially in simply switching magnets, the simplest possible geometry of the adapter piece should be employed in the production.
Examples for how an armature in cooperation with a pole piece can be contoured are given in German Patent Disclosure DE 103 27 875 B4. However, in terms of production, this discloses pole pieces of quite complicated shape.
In conventional, easy to manufacture solenoids, the characteristic force-travel curve at present usually does not have an optimal course. Specifically, for actuating hydraulic switching valves or proportional valves, even at short to medium strokes of the control piston, strong flow forces, oriented counter to the actuation, must be overcome and they increase only slightly in the further course of the stroke. Moreover, the flow forces are often effective over only a narrowly defined portion of the stroke. Conversely, conventional solenoids develop a strong force only in the final portion of the stroke. Aside from this, the force development is not very localized and is usually embodied as uniform or with a slight ascending slope over a wide stroke range. This requires large solenoids, with correspondingly high consumption of material and energy.